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<p> The <em>IfcDuration</em> identifies a quantity of time (or a "lenght" of an event occurring in time).
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<p>This lexical representation for <em>IfcDataTime</em> is PnYnMnDTnHnMnS, where nY represents the number of years, nM the number of months, nD the number of days, 'T' is the date/time separator, nH the number of hours, nM the number of minutes and nS the number of seconds. The number of seconds can include decimal digits to arbitrary precision.
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<blockquote class="example">
EXAMPLE&nbsp; P2Y10M15DT10H30M20S (duration of two years, 10 months, 15 days, 10 hours, 30 minutes and 20 seconds).
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<blockquote class="note">
NOTE&nbsp; See extended format representation of <strong>duration</strong> as defined in ISO&nbsp;8601. The restrictions defined in XML Schema Part 2 apply.
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<blockquote class="history">HISTORY&nbsp; New type in IFC4</blockquote>

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